As is well known, the lighter body, or socket, of a cigar lighter acts as a power point or current supply element, in that it serves both as a receptacle for a heater plug, for lighting cigars or cigarettes, and as a socket into which a plug of an accessory may be inserted.
To this end, the lighter body, for receiving a removable heater plug, includes for this purpose an electrically conductive lighter body sleeve having a base portion, on either side of which there are mounted, firstly, within the said sleeve, a two-fingered clip and a first electrically insulating member, referred to as a first insulating ring, and secondly, on the outside of the said body sleeve, an electrical power supply tongue, referred to as a second power supply tongue and associated with the said body sleeve, with a second electrically insulating member, referred to as a second insulating ring, being interposed axially between the second power supply tongue and a further electrical power supply tongue referred to as the first power supply tongue, the first power supply tongue being associated with the two-fingered clip and being connected electrically to the said clip by means of a fastening member which assembles the clip, the insulating rings and the power supply tongues to the base portion of the body sleeve, the cigar lighter further including a protective device for giving protection against overheating.
It is common practice to provide a device for giving protection against overheating. In this connection, under some circumstances the fingers of the two-fingered clip may remain in engagement with the end cup element of the heater plug, even after the heater plug has reached the required temperature. In addition, a short circuit can sometimes occur. These conditions can cause a fire, a danger which is aggravated by the fact that the lighter body is normally secured on a fixed wall of the vehicle, which is commonly made of a plastics material.
It has been proposed, accordingly, in French patent specification No. FR 2 338 822A, to give the first insulating ring a recess in which a fusible body is mounted. This body, or fuse, melts at a predetermined temperature, and sets up a short circuit.
It is similarly possible to cause a short circuit by means of a generally L-shaped safety tongue, which is interposed between the base portion of the body sleeve and the second power supply tongue. This safety tongue makes electrical contact with the first power supply tongue in the event of overheating, in the manner described in International Patent publication No. WO95/19273.
These arrangements are not entirely satisfactory, because they make it necessary to change the fuse on the fascia panel, or the like, in which the cigar lighter is mounted. In addition, their nature is such that they increase the axial distance between the two-fingered clip and the base portion of the lighter body sleeve, and the latter is then also of a non-standard type.
It might also be considered that the protective device could be incorporated into the heater plug, but this would involve modifying the latter. In addition, when a plug is inserted into the lighter body, the protection would be lost.
U.S. patent specification No. 4,459,464, and German patent specification DE 40 42 043A, for example, disclose arrangements in which the protective device is fitted on the outside of the lighter body sleeve. In that case, only one power supply tongue is provided, namely the first tongue which is associated with the two-fingered clip, the first tongue being insulated from the base of the lighter body sleeve by the second insulating ring in contact with the body sleeve base. This first tongue serves for fastening one of the ends of a fuse, the other end of which is fixed to a supplementary component, separate from the first tongue, by means of a third electrical insulating ring.
This supplementary component serves as an abutment for a resilient ring which is associated with a nut of the fastening member, the latter being in this case in the form of a bolt. None of this is applicable to an arrangement having two power supply tongues carried by the base portion of the lighter body sleeve. In addition, the fuse is not physically protected, and it can become damaged during handling before the lighter body is fixed on the fixed wall of the vehicle. And even after the lighter body has been fitted on this fixed wall, the fuse can still be damaged, for example by a connecting wire, in view of the fact that the lighter body is fitted in an environment where there are numerous other items of equipment.